The invention is directed to a solid antimicrobial product especially suited for the preservation of organic material and for combating detrimental microorganisms, as well as for pH control. The invention is also directed to a method for producing a solid antimicrobial.
In the description of the background of the present invention that follows reference is made to certain structures and methods, however, such references should not necessarily be construed as an admission that these structures and methods qualify as prior art under the applicable statutory provisions. Applicants reserve the right to demonstrate that any of the referenced subject matter does not constitute prior art with regard to the present invention.
Aqueous solutions of formic acid are known to be strongly corrosive solutions. The handling and storage of such solutions requires acid-resistant materials. This is a problem in industrial processes and agriculture where feed preservative solutions that contain formic acid are used. Machinery and equipment coming into contact with the solutions are subject to corrosion. Thereby their useful life is shortened, which causes extra costs to the industry and farmers.
Attempts have been made to find a solution to the problem by adding to an aqueous solution of formic acid substances that reduce corrosion. From EP application 411 827 there is known a feed preservative solution that contains formic acid and octanoic acid, and additionally possibly propionic acid and ammonia. However, the publication contains no mention of what the reduced corrosive action is based on.
FI patent 61790 discloses an aqueous solution containing formic acid and a cation. The ratio of the acid to the cation is 2:1-4:1, calculated on the basis of the chemical equivalents, and the water content is 15-90%, indicated in percentages by weight.
International application WO-99/00023 presents, as a solution to the problem, the neutralization of an 85% aqueous solution of formic acid with a base, such as ammonia, at an acid to base cation ratio higher than four, calculated on the basis of the chemical equivalents.
According to one known method, an aqueous solution of a formic acid complex salt is absorbed into supports. In EP application 009 366, there is added as a stabilizing agent to a milk-containing animal feed a 75% aqueous solution of a complex salt, absorbed into a support, the aqueous solution containing, for example, ammonium ions and formic acid at a ratio of 2:1-4:1. In this case the support is impregnated with a large quantity of water, while the quantity of the active agent remains low.
Through state-of-the-art solutions it has been possible to reduce the corrosion caused by formic acid. However, corrosion still causes financial losses and complicates the handling of the solutions. Owing to the high vapor pressure of formic acid, the handling of formic acid solutions is a problem even at low temperatures. The acid solutions are also quite corrosive.
An object of the present invention is to provide a product that contains as concentrated an amount as possible of the active agent, formic acid, but simultaneously have little corrosive action, and additionally the use of the product would be easy and safe.
Another object of the invention is to provide a method by which first a water-free formic acid can be ammoniated and then a solid product can be prepared.
By means of the present invention there is thus provided a product which has a reduced corrosive action and the handling of which is less hazardous to the environment than the handling of known products. The product contains partly neutralized water-free formic acid, which has a lower vapor pressure than non-ammoniated acid, whereby environmental hazards are reduced. Occupational hygiene is improved, since adverse odors and irritation are reduced.
According to one aspect, the present invention encompasses a solid antimicrobial product comprising: a concentrated formic acid partly neutralized with gaseous ammonia and having a water content less than 2% by weight absorbed in a support.
According to another aspect, the present invention encompasses a method for the production of a solid antimicrobial product, the method comprising forming a concentrated formic acid having a water content below 2% by weight, directing gaseous ammonia at the formic acid to render a formic acid to ammonium ion molar ratio of 3:1-38:1 and the partly neutralized formic acid, and contacting the partly neutralized formic acid with a support.
A study of aqueous solutions of formic acid showed that aqueous acids are more corrosive than water-free formic acid. It was observed, unexpectedly, that by the use of a nearly water-free formic acid, having a water content below 2% by weight, it was possible to reduce corrosion considerably. In order to reduce corrosion, concentrated formic acid was further partly neutralized with gaseous ammonia, thus avoiding the passing of extra water into the product. In order to facilitate the handling of the product, the obtained ammoniated formic acid concentrate was absorbed into a support, causing as large an acid amount as possible to be absorbed into the support and at the same time reducing the amount of support. The solution according to the invention thus provides an additional advantage in cost saving, since supports as such are considerably more expensive than is formic acid itself. It has been possible to impregnate the same support amount with a maximum amount of active agent. At the same time the storage and transport costs have been reduced, since the product amounts/active agent are in a compact form.
The tests carried out also showed that the formic acid product according to the invention has a lower freezing point than has a non-neutralized water-free formic acid. This enables a liquid product to be transported and used at quite low temperatures even in winter without a risk of freezing. Likewise, the storage of the raw material is facilitated, since heated storage containers are not necessary.
The active agent in the product according to the invention is a nearly water-free formic acid. The water content of the formic acid must be below 2% by weight. Gaseous ammonia is used for the neutralization of the acid. The formic acid to ammonium ion molar ratio recommended for the solution thus obtained is 3:1-38:1, and an especially preferable range is 5:1-12:1. These ratios have been calculated on the basis of the chemical equivalents.
According to the invention, the partly ammoniated formic acid is absorbed into a support. The impregnation can be done, for example, by spraying the acid into a mechanically fluidized support. The support may be pulverous, porous or granulated. Both inorganic and organic inert support raw materials are suitable for use as the support. An inorganic support may be, for example, vermiculite, perlite, silica, alumina, clay, diatomite, or kaolin. An organic support may be, for example, soy powder, corn-cob fractions, a microbial protein, dried sugar cane pulp, or citrus tree pulp. The most important factors affecting the choice of the support include a high adsorption/absorption capacity and the absence of health hazards.
In the solid product according to the invention, the weight ratio of the formic acid to, the support is preferably within the range 0.25:1-9:1.
According to the invention, the partial neutralization of water-free formic acid is preferably carried out in a special reactor-cooler system. Gaseous ammonia is added under precisely controlled conditions, for example, via an ejector into a pressurized reactor that contains the water-free formic acid. Since the reaction is strongly exothermal, the solution must be cooled. This can be done advantageously, for example, by cycling the solution via an outside cooler back to the reactor. The temperature is maintained under control by controlling the ammonia fed in and by cooling the cycle. The final result obtained is a formic acid solution having the desired ammonium formate concentration.
The product according to the invention is suited for use as an antimicrobial agent for the preserving of an organic material and for combating detrimental microorganisms. An especially suitable use is the preservation or pH control (lowering) of feeds intended for animal consumption, such as complete feed, its components, green forage, soilage, and grain. Below, the invention is illustrated with examples.